or they call them challenges because the knew if they would call them "daily quests" people would immediately complain that the Chateau doesn't boost it with the argument that they are quests and so it must be boosted by the chateau
or completely different
if you look closely you see that you open a chest
so to be accurate you don't get coins
you get a chest which then give you coins
reward (as you can see on the screenshot): a chest
and the chateau obviously doesn't boost chests
yes lets answer it again by some more trustworthy person
Well, calling them challenges instead of quests just to avoid having the Chateau boost apply seems underhand to me. However I think they call them challenges just for variety, and because they are more difficult to complete. Else people would likely complain that these new quests (tasks) are too difficult, to which they can reply that they are supposed to be difficult [as mentioned in the announcement] that is why they are called challenges (they are supposed to be challenging).
As for the chest aspect, it depends. As I have said I do not have this new feature myself yet, so I only go by the screenshots in the announcement, and by what someone else reported earlier (that they got coins as a reward).
The weekly reward (for doing all 7 challenges in a week) seems to be indeed a chest that contains a special building or reno kit etc (the very desirable items). I do not know if one will know in advance what is inside the challenger's chest for the current week or not. But as the rewards are special items, Chateau would not apply anyway (chest or no chest).
For the daily challenges, you first choose a chest for the day from the two available. I do not know how the reward (contents of chosen chest) is then displayed along the task/quest instructions. But as mentioned by someone who tried it, one option was a coin package (so should be Chateau-boostable) and the other chest had probabilities of various things, one of which was a coin package (which could/should be boostable).
So similar to the recurring quests which give random rewards it is not known in advance if the reward will be boosted. If you get coins they will be boosted, but if you get BP's they won't be.
Hopefully we can get a definitive answer soon. And I honestly hope they are boosted, since once you go past the early ages (up to Colonial), one cannot do many recurring quests, so chateau becomes less useful. If it at least boosts some of the daily challenges rewards, that would help a bit towards justifying the space it takes and the FP's invested in it.